1. Field of the Invention
The present invention relates to a liquid crystal display panel, liquid crystal display device, photo detecting device and light intensity adjustment method; in particular, the present invention relates to a liquid crystal display panel, liquid crystal display device, photo detecting device and light intensity adjustment method applicable for detecting a light source and outputting a multi-bit digital signal corresponding to the intensity of the light.
2. Description of Related Art
Ambient Light Sensing (ALS) may be applied to improve the efficiency of energy management in display devices and enhance viewing quality of applications like televisions, screens, Digital Photo-Frames (DPF), notebook computers, mobile phones, personal navigation device and media players, thereby effectively enabling reduction of power consumption and extension of life span in batteries thereof. For example, the longer time the backlight in a liquid display illuminates, and the more power it consumes. Therefore, through automatic detection on ambient light as well as adjustment to the backlight brightness based on the variation in ambient light, it is possible to achieve intelligent control and lessen power consumption.
The aspect of management for automatic ambient light sensing lies in that it allows spontaneous adjustment for overly bright or overly dark screens according to settable light source feature data, further lowering current dissipation and prolonging battery usable duration, especially regarding to enhancement of efficiency for power utilization on handheld electronic devices as well as provision of clear screen viewing for users. In the prior art, in order to enable a display device with such an ambient light sensing function, it is required to compose an additional sensor module onto the display device. Such an approach may cause undesirable increases in the number of parts and fabrication cost, and miniature or slimness of display devices may not be successfully achieved.
The conventional ambient light sensor generates a photo current under photo excitement by means of photodiode, then the generated photo current is amplified in gains to an operable range through an amplifier; after computation performed by the analog-to-digital converter (ADC), the control signal is sent to the backlight controller for dimming.
However, the conventional ambient light sensor inevitably generates a dark current which adversely affects a signal/noise (S/N) ratio, and such an impact becomes significant upon low lux levels; meanwhile, the dark current fluctuates dramatically when temperature varies, so poor the S/N ratio may occur when used under higher temperature. As a result, in order to effectively read the signal generated by such type of highly sensitive light sensor, it needs to use more sophisticated amplification and ADC conversion circuit design, e.g. additionally disposed a compensation circuit or dark current elimination circuit, thus also undesirably increasing fabrication cost.